Legionella pneumophila is the etiologic agent for a recently recognized and described form of acute pneumonia. Since its isolation less than three years ago, this bacterium has been the subject of extensive research in many areas of investigation. Only recently, however, has information begun to emerge which hints at the natural habitat of this bacterium, how it is transmitted to humans, and how it is able to cause disease. An association with the water in air-conditioning systems, and the isolation of the bacterium from nonepidemic environmental water sources has suggested that the bacterium is ubiquitous in nature, but these studies did not define the physical and nutritional parameters of the habitat. This proposal is designed to provide a better understanding of the overall metabolic capabilities of this organism, and to determine the conditions (nutritional, physical, etc.) under which this bacterium is able to survive and/or grow in the environment. Using a chemically defined medium, we will investigate the specific nutrient requirements for growth. Corroborative data will be obtained by analyzing the incorporation of radiolabeled compounds into cellular components, oxidation of compounds as energy sources, and measurement of enzyme activities associated with these processes. We will also study various parameters of the survival of starvation in water or other aqueous environments. Variables to be studied include the influence of cell density and cellular morphology,presence of certain inorganic compounds, and the role of the storage polymer poly-Beta-hydroxybutyrate.